As mobile devices have been increasingly developed, and the demand of such mobile devices has increased, the demand of secondary batteries has also sharply increased. Among them is a lithium secondary battery having high energy density and operating voltage and excellent preservation and service-life characteristics, which has been widely used as an energy source for various electronic products as well as for the mobile devices.
Based on their external and internal structures, secondary batteries are generally classified into a cylindrical battery, a prismatic battery, and a pouch-shaped battery. Especially, the prismatic battery and the pouch-shaped battery, which can be stacked with high integration and have a small width to length ratio, have attracted considerable attention.
Also, the secondary batteries have attracted considerable attention as an energy source for electric vehicles and hybrid electric vehicles, which have been developed to solve problems, such as air pollution, caused by existing gasoline and diesel vehicles using fossil fuel. As a result, kinds of applications using the secondary batteries are being diversified owing to advantages of the secondary batteries, and hereafter the secondary batteries are expected to be applied to more applications and products than now.
However, various combustible materials are contained in the lithium secondary battery. As a result, there is a possibility of danger in that the lithium secondary battery can be heated or explode due to overcharge, overcurrent, or any other external physical impacts. In other words, the lithium secondary battery has low safety. Consequently, a protection circuit module (PCM) for effectively controlling the abnormality of the lithium secondary battery, such as overcharge, is mounted in the lithium secondary battery while the PCM is connected to a battery cell of the lithium secondary battery.
Generally, it is required for safety elements, including the PCM, to be maintained in electrical connection with electrode terminals of the battery cell and, at the same time, to be electrically isolated from other parts of the battery cell. Consequently, a plurality of insulative mounting members are required to construct such connection, with the result that the battery assembling process is complicated. Also, an adhesive may be applied between the safety elements and the insulative mounting members to achieve the coupling between the safety elements and the insulative mounting members. However, this coupling method weakens the strength of the battery. Consequently, a short circuit may occur in the battery cell due to the weakening of the coupling strength, when external impacts are applied to the battery cell, with the result that the battery cell may catch fire or explode. In other words, safety-related problems may occur.
Therefore, research has been actively made on technologies for easily assembling the insulative mounting members and the safety elements loaded on the top of the battery cell and, at the same time, increasing the mechanical strength of the battery pack. For example, Korean Patent Application Publication No. 2006-0027272 discloses a battery pack including a bare cell, a protection circuit board electrically connected to the bare cell, a case integrally coupled to the bare cell and the protection circuit board such that a predetermined region of the bare cell is exposed outward through the case, and a resin for covering the bare cell exposed outward through the case. Also, Japanese Patent Application Publication No. 2007-165328 discloses a battery constructed in a structure in which an external connection terminal is formed at the outer circumferential part of one side of a battery body, a circuit board, as a protection circuit element, is mounted to the other side of the outer circumferential part of the battery body, a cathode and an anode of the battery body are electrically connected to the circuit board by connection members, at which heat sensitive element are arranged, wherein a mold having the connection members, the battery body, and the circuit board disposed therein is filled with resin to form a mold body attached to arbitrary surfaces of the battery body and the circuit board to integrate the battery body and the circuit board.
In the above-described technologies, however, a process for filling the space defined between the electrode terminals and the protection circuit board at the top of the battery pack with resin is added, with the result that the manufacturing process is complicated, and the weight of the battery pack is increased. Furthermore, the improvement in mechanical strength of the battery pack does not come up to expectations.
Consequently, there is a high necessity for a technology that is capable of reducing the number of members mounted to the top of the battery cell to simplify the assembling process and achieving the connection between the connection members, the mounting member, and the protection circuit board in a no-welding manner while simultaneously stably securing a coupling strength.